This kmz file shows the extent of coverage for the August 2010 USACE Maryland lidar
data set.

These files contain topographic lidar data classified as ground (2) and unclassified
(1) in accordance with the American Society for Photogrammetry and Remote Sensing
(ASPRS) classification standards. These data were collected by the Compact Hydrographic
Airborne Rapid Total Survey (CHARTS) system along the coast of Maryland. CHARTS integrates
topographic and bathymetric lidar sensors, a digital camera and a hyperspectral scanner
on a single remote sensing platform for use in coastal mapping and charting activities.
Data coverage generally extends along the coastline from the waterline inland 500
meters (topography) and offshore 1,000 meters or to laser extinction (bathymetry).
The topographic lidar sensor has a pulse repetition rate of 9 kHz at 1064 nm (near-infrared
wavelength). The bathymetric lidar sensor has a pulse repetition rate of 1 kHz at
532 nm (green wavelength). Native lidar data is not generally in a format accessible
to most Geographical Information Systems (GIS). Specialized in-house and commercial
software packages are used to process the native lidar data into 3-dimensional positions
that can be imported into GIS software for visualization and further analysis. Horizontal
positions, provided in decimal degrees of latitude and longitude, are referenced to
the North American Datum of 1983 (NAD83). Vertical positions are referenced to the
NAD83 ellipsoid and provided in meters. The National Geodetic Survey's (NGS) GEOID03
model is used to transform the vertical positions from ellipsoid to orthometric heights
referenced to the North American Vertical Datum of 1988 (NAVD88). The 3-D position
data are sub-divided into a series of LAS files, each covering approximately 5 kilometers
of shoreline. The file index is provided by the shape file, "md_boxes.shp", and the
numbers used to identify files are in the "Box" field of the shape file. The LAS file
naming convention is based on the year, project, area name, "Box," and the product
type. An example file name is "2010_NCMP_MD_Aug_03_GeoClassified.las", where 2010
is the year of data collection, NCMP is the project under which data were collected,
MD is the area of data collection, 03 is the "Box" number and "GeoClassified" is the
product type. The format of the file is LAS version 1.1.

DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National
Oceanic and Atmospheric Administration, U.S. Department of Commerce

Date(s)

publication: inapplicable

Data Presentation Form:

Digital image

Dataset Progress Status

Complete

Data Update Frequency:

As needed

Purpose:

These data were collected as a part of the NCMP to depict the elevations above the
water in the Maryland coastal zone.

Use Limitations

These data depict the elevations at the time of the survey and are only accurate for
that time. Users should be aware that
temporal changes may have occurred since this data set was collected and some parts
of this data may no longer represent actual surface
conditions. Users should not use this data for critical applications without a full
awareness of its limitations. Any conclusions drawn
from analysis of this information are not the responsibility of NOAA or any of its
partners. These data are NOT to be used for navigational purposes.

These data were collected using the CHARTS system. It is owned by the Naval Oceanographic
Office and operated through contract. The system collects topographic lidar data at
9kHz, bathymetric lidar data at 1kHz and RGB imagery at 1Hz. A CASI-1500 hyperspectral
line scanner is integrated with the system as well. Aircraft position, velocity and
acceleration information are collected through a combination of Novatel and POS A/V
410 equipment. All raw data streams are transferred to the office for downloading
and processing in SHOALS GCS software. Aircraft position data are processed using
POSPac software and the results are combined with the lidar data to produce 3-D positions
for each lidar shot. Upon inspection and QA/QC in the software packages Fledermaus
and PFM_ABE, anomalous data are flagged as invalid. PFM_ABE's chartsLAS module then
converts all valid data from ellipsoid to orthometric heights based on the NGS' GEOID03
model and exports topographic data as a series of LAS files with a single file per
flightline per 5km box.

The flightline LAS files are imported into the TerraScan V11 module within MicroStation
V8.0. The resulting LAS files are thinned to eliminate duplicate points. A customized
classification macro is used to distinguish ground points (2) and unclassified points
(1). The classification results are QC'd and any misclassified points are manually
edited. In areas of dense vegetation the bare ground points might be incorrectly classified
due to the inability of the laser to penetrate the canopy and reach the bare ground.
In these areas, JALBTCX defaults to the algorithm's "ground" surface instead of manually
reclassifying those points. The points are exported to an ASCII file containing the
following fields: longitude, latitude, elevation (orthometric), intensity, classification,
mirror angle, time (GPS time), number of echos, and echo number. The ASCII file is
converted to LAS with the txt2las code from LAStools (<http://www.cs.unc.edu/~isenburg/lastools/>).

The NOAA Coastal Services Center (CSC) received data in LAS v1.1 format. The files
contained LiDAR elevation and intensity measurements. The data were received in geographic
coordinates (NAD83) and vertically referenced to NAVD88 using the Geoid03 model. The
vertical units of data were meters. The data were classified according to ASPRS LAS
classification scheme (1 = unclassified, 2 = ground). CSC performed the following
processing for data storage and Digital Coast provisioning purposes: 1. The LAS files
were converted from orthometric heights to ellipsoidal heights (GRS80) using Geoid
03. 2. The LAS data were sorted by latitude and the headers were updated. 3. The data
were converted to LAZ format.

The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp
transfer from the NOAA Coastal Services Center. The data are currently
being served via NOAA CSC Digital Coast at http://www.csc.noaa.gov/digitalcoast/.
The data can be used to re-populate the system. The data are archived in LAS or LAZ
format.
The LAS format is an industry standard for LiDAR data developed by the American Society
of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless compressed version
of
LAS developed by Martin Isenburg (http://www.laszip.org/). The data are exclusively
in geographic coordinates (either NAD83 or ITRF94). The data are referenced vertically
to
the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most
up to date geoid model when transforming to orthometric heights.